High-voltage generating device of the type described has been broadly used mainly for ignition in cigarette lighters and so forth. In recent years, there is an increasing demand for this kind of device to operate with reduced force at higher ignition reiability, as well as to exhibit higher durability.
A conventional high-voltage generating device will be explained hereinunder with reference to FIGS. 1 to 3. As shown in FIGS. 1 and 2, the high-voltage generating device has an outer case 1 in which is defined a bore 1a for accommodating a piezoelectric element and having a volume which is about 1.2 times as large as the volume of the piezoelectric element. The piezoelectric element 2 together with an anvil member 3 is inserted into this bore 1a through an element insertion hole 1b formed in the side bottom surface of the outer case 1, and a support member 4 is inserted into the bore 1a through a top opening in the outer case 1. Then a pressing spacer 5 is inserted into the bore 1a such as to firm the contact between the piezoelectric element 2, anvil member 3 and the support member 4. In this state, an adhesive 6 which has a comparatively low bonding strength and setting hardness, e.g., a silicon resin, is charged into the bore such as to fix the piezoelectric element 2 together with the anvil member 3 and the support member 4. A return spring 7 is loaded in a space 1c within the outer case 1 on the front side of the anvil member 3 and, thereafter, an inner case 11, which accommodating a striking mechanism including a striking spring 10, striking pin 8 and a striker 9, is slidably inserted into the outer case, thus completing the assembly of the high-voltage generating device. For further detail of this known device, a reference shall be made to Japanese Utility Model Laid-Open Nos. 142558/1983 and 124856/1984.
The operation of this known high-voltage generating device is as follows. As the inner case 11 in the outer case 1 is slided in the direction of an arrow B overcoming the force of the return spring 7, striking energy is stored in the striker 9 because the striker pin 8 is engaged by a cam formed in the case 1. As the inner case 11 is further slided, the striker pin 8 secured to the striker 9 is disengaged from the cam on the outer case 1, by the action of a cam which is formed in the inner case 11. In consequence, the striker 9 strikes the anvil member 3 by the energy stored therefor.
In consequence, an impact strain is caused in the piezoelectric element 2 so that the latter generates a high voltage. This high voltege is supplied through a high-voltage lead (not shown) connected to the support member 4 to a discharge gap, such as to ignite, for example, the fuel of a cigarette lighter. Then, as the outer case 1 is released from the pressing force, the inner case 11 is returned to the initial position together with the striker 9 by the force of the return spring 7.
In this known high-voltage generating device, the adhesive 6 for insulating the piezoelectric element 2 and fixing the same to the outer case 1 is made of, for example, a silicon resin having comparatively low bonding strength and setting hardness. In addition, the layer of the adhesive covering the piezoelectric element is extremely thin, and the outer case 1 is made of a polypropylene or an ABS resin which contains no reinforcement agent and which exhibits only a small affinity to the adhesive. In consequence, when the impact is applied, only the piezoelectric element 2 is vibrated for a short period T.sub.1 as shown in FIG. 3, so that only a small discharge area is available as shown by hatched area in FIG. 3. In addition, this known device does not exhibit high durability bacause of small adhesive layer thickness and small bonding strength.
When this high-voltage generating device is mounted in a cigarrette lighter for example, it is necessary that the high-voltage lead is connected to the support member 4 in order to deliver the high-voltage generated by the piezoelectric element to the outside and that the connecting portion is electrically insulated. This inconveniently impairs the handling of the cigarrette lighter.
In view of the above-described problems of the prior art, the present invention aims at providing a high-voltage generating device which is capable of converting an impact energy imparted to the piezoelectric element into electric energy at a high efficiency such as to obtain a high energy, thereby attaining a high ignition reliability and easy operation, as well as a high durability and easy pick-up of the high voltage generated by the piezoelectric element.